The most important capability of a Third Generation (3G) system is the capability of supporting high speed mobile packet services. Wide Code Division Multiple Access Release 99 (WCDMA R99) may provide a data rate up to 2 Mbps peak, which is sufficient for most existing packet services. For many data services with higher traffic and delay requirements, such as video, stream media and downloading services, however, the system is required to provide a higher transmission rate and a shorter delay.
Third Generation Partnership Project Release 5 (3GPP R5) introduces a High Speed Downlink Packet Access (HSDPA) technology, which not only supports high speed asymmetrical data services, but also may minimize the cost of the operators while improving the network capacity. HSDPA provides a stable approach for evolution of Universal Mobile Telecommunications System (UMTS) which has a higher data transmission rate and a higher capacity. With a full reference to the general idea and experiences of CDMA 2001X EV-DO, the HSDPA technology presented in R5 adds a new High Speed Downlink Shared Channel (HS-DSCH), to enable the centralized utilization of resources, such as transmission power, pseudo-noise (PN) code, as well as the dynamic allocation of the resources according to the practical condition of users, thereby the availability of resources may be improved.
During the transmission of single-carrier downlink packet data according to Release 5 specifications, HSDPA traffic channels and control channels are established by the following steps of: a1, determining channel resources required by HSDPA; a2, finding channel resources satisfying a condition of a cell; a3, allocating these channel resources for HSDPA to be traffic channel, e.g. HS-DSCH, as well as uplink and downlink control channels (High Speed Shared Information Channel, HS-SICH, and High Speed Shared Control Channel, HS-SCCH). The minimum unit of a channel resource is the combination of timeslot resource and code channel resource. When accessing a network, a user terminal obtains the resource information of its traffic channels as well as uplink and downlink control channels from the network. During data transmission, the network sends, via an HS-SCCH, control information required by the user terminal for receipt of packet data, schedules packet data according to data transmission answer acknowledge messages fed back by an HS-SICH and sends the packet data via the HS-DSCH. In this way, the user terminal is enabled to receive the packet data transmitted via the HS-DSCH according to the control information transmitted via the HS-SCCH.
During the above described downlink data transmission, the traffic channel and the control channels are borne over one carrier. As a result, the peak rate for transmitting data by use of HSDPA is limited by the channels, particularly when the carrier has limited HSDPA resources.
How to improve the peak transmission capacity in data transmission? In the prior art, a higher-order modulation is generally applied to a transmission signal, or the Multiple In Multiple Out (MIMO) or Orthogonal Frequency Division Multiplexing (OFDM) technology may be used, so as to enhance the HSDPA data transmission rate. However, for HSDPA in which the power of the transmission signal is limited, the application of the higher-order modulation may reduce the coverage scope of the higher-order-modulated signal. Moreover, the higher-order-modulated signal generally imposes higher requirements on devices, such as a power amplifier and a signal processor. Furthermore, for new physical layer technologies such as MIMO or OFDM, this technology is not matured currently. As a result, using this technology may result in a long developing period, a high cost and a high risk, and therefore is not the best choice for enhancement of peak transmission capability in data transmission at present.
In other words, with the existing downlink packet data transmission methods, it is difficult to further improve the peak transmission rate of user packet data. The applicant suggests employing multi-carrier HSDPA technology to enhance the transmission capability of packet data traffic. Whereas the current R5 specifications employ the single-carrier transmission of HSDPA, in which the channel establishment for control channels (HS-SCCH, HS-SICH) and traffic channel (HS-DSCH) is relatively simple, which does not meet the requirements of multi-carrier transmission of HSDPA.